Tuning device for wireless receivers



' June 6, 1933. I c. E. G. BAILEY TUNING DEVICE FOR WIRELESS RECEIVERS Filed Jan. 6, 1930 czwzz elwmwecwa AITTORNIJG Patented June 6,1933

UNITED STATES PATENT o FFICE 1 onarsrornna EDMUND GERVASE, BAILEY, or LONDON, ENGLAND, ASSIGNOR T0 vro'ron TALKING MACHINE co PANzA CORPOR TION 01* NEW JERSEY TUNING DEVICE no Application flledfJ'anuary 6,1930, Serial No.

The present invention relates to the tuning devices of wireless rece vers in which it is desired totune two or more separate circuits by means of ganged or mechanlcally interconnected controls.

' Ina supersonic hetero dyne receiver, for example, in whicha frame aerial is used, the frequencies of the oscillator and the main tuning circuitsare connected by the relation that there must be a constantdifierence be tween them, namely the so-called intermediate frequency. If tuning condensers are used for tuning these two circuits with the blades so shaped that the angular movement ofthe dial is a linear function of the he quency, there will be a constant differencebetween the angular positions of these condensers when the set is in tune, provided that the same angular position of both of them corresponds to the same frequency. If the condensers are similar, this last condition. is only fulfilled if the inductance of the frame aerial circuit is equal to the inductance of the oscillator coil, and if there 13 no distributed capacity in the circuit not al lowed for in the shaping of the condenser blades. If these conditions are fulfilled, the two condensers may be operated from a common shaft.

invention is applied to these receivers, the

setting of the compensating device may remain substantially constant throughout the range of the tuning condensers. In practice itmay, however, be found necessary to vary the adjustment of the compensating device overthe lower 10% of the tuning range.

The variable inductance may either be of a WIRELESS nncmvnns 418,930, and in Great Britain January 9, 1929".

In both the circuit arrangements in the drawing the invention is shown applied to a supersonic heterodyne receiver embodying a valve acting simultaneously as first detector and oscillator.

Figure l ofthe drawing is a diagrammatic view of a preferred embodiment of my invention, and I Figure 2 is a diagrammatic view of a circuit including an alternative form of my invention.

Referring to Fig. 1 of the drawing, a frame aerial 1 has connectedin series with it a small I variometer 2 and the whole is shuntediby a variable tuning. condenser 3.

One terminal of the tuned circuit 1, 2, 3 is connected through a fixed condenser 4 to the mid-point of a grid circuit inductance ,5

which is shunted by a second variable tuning 1 valve 7. One end of the inductance 5 is connectedthrough a high resistance 8 to the fila ment of thelvalve 7 and the other end of the inductance 5 is connected to the grid of the valve 7. The anode of the valve 7 is connected through an inductance 9, coupled to 7.

the gridcircuit inductance 5, to a source of high tension supply 10, the negative terminal of which is connected to the filament of the valve 7 I The coupling of the two inductances 5, 9 is so arranged as to produce oscillations of the valve 7. The remainder of the circuit may be arranged. in any known or suitable C2 is shown arranged in series with thegrid manner. In Fig. 2, the variable inductance circuit inductance 5 instead of in the aerial circuit, other connections being the same as in Fig. 1. I

In a modification of the above arrangements the variometer 2 is omitted and, instead, a relatively large variometer is connected in shunt with either the frame aerial 1 or the grid circuit inductance 5.

I claim:

1. In combination, a thermionic oscillator having an input'inductor provided with tuning means, a receiving network provided with tuning means, a connection including a reactor between one terminal of said network and an intermediate point on said input inductor, means for simultaneously adjusting both of said tuning means to provide a substantially constant frequency difference, and a compensating device in the form of a variable inductor associated with at least one of said tuning means.

2. In combination, a thermionic tube, an input inductor therefor, terminals of said inductor beingconnected, respectively, to the grid of said tube and to the cathode thereof, a resistor in said last-named connection, tuning means for said inductor, a receiving network provided with tuning means, a connection including a reactor between one terminal of said-network and an intermedlate pomt on said lnput inductor, means for S1- multaneously adjusting both of saidtuning means to provide a substantially constant frequency difference, and a compensating device in the form of a variable inductor associated with at least one of said tuning means.

3. The invention set forth in claim 2 characterized in that the compensating device is associated with the input inductor.

4. The invention as set forth in claim 2 characterized in that the compensating device is associated with the receiving network.

5. In combination, a frame aerial, a variable inductor connected in'series therewith, a tuning condenser connected in shunt thereto, a thermionic tube having an input circuit, an input inductor therefor, a tuning condenser connected in shunt with said input inductor, a connection including a fixed condenser between a point on the frame aerial and an intermediate point on said input inductor, mechanical coupling means interconnecting said tuning condensers, and a connection from another point on said frame aerial to the cathode of said thermionic tube.

6. The invention as set forth in'claim 5 characterized in that one terminal of the input inductor is connected directly to the whereby energy from the output circuit of said tube is transferred to the input circuit thereof to cause the generation of oscillations.

8. In combination, a frame aerial, a tuning condenser connected in shunt thereto, a thermionic tube, an input inductor for said tube, a. tuning condenser connected in shunt to said input inductor, means interconnecting said tuning condensers for simultaneous operation, a connection including a coupling condenser between a point on said frame aerial and an intermediate point on said input inductor, a further connection from another point on said input inductor to the cathode of said tube, and a compensating variable inductor serially included in the circuit constitutedby said input inductor and the tuning condenser connected in shunt thereto.

9. The invention set forth in claim 8 characterized in that one terminal of said input inductor is connected to the cathode of said tube over a resistor.

10. The invention set forth in claim 8 characterized in that means are provided whereby said tube is caused to generate oscillations.

,In testimony whereof I have signed my name to'this specification.

HRISTOPHER EDMUND GERVASE BAILEY. 

